package com.miao.hong.fang.util.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class SetCharacterEncodingFilter implements Filter{


    // ----------------------------------------------------- Instance Variables

    /**
     * The default character encoding to set for requests that pass through this filter.
     */
    protected String encoding = null;

    /**
     * The filter configuration object we are associated with. If this value is null, this filter instance is not
     * currently configured.
     */
    protected FilterConfig filterConfig = null;

    // --------------------------------------------------------- Public Methods

    /**
     * Take this filter out of service.
     */
    public void destroy() {
        this.encoding = null;
        this.filterConfig = null;
    }

    /**
     * Select and set (if specified) the character encoding to be used to interpret request parameters for this request.
     * 
     * @param request
     *                The servlet request we are processing
     * @param response
     *                The servlet response we are creating
     * @param chain
     *                The filter chain we are processing
     * 
     * @exception IOException
     *                    if an input/output error occurs
     * @exception ServletException
     *                    if a servlet error occurs
     */
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException,
            ServletException {
        // Select and set (if needed) the character encoding to be used
        String encoding = selectEncoding(request);

        if (encoding != null) {
            request.setCharacterEncoding(encoding);
            //response.setCharacterEncoding(encoding);
        }

        // Pass control on to the next filter
        chain.doFilter(request, response);
    }

    /**
     * Place this filter into service.
     * 
     * @param filterConfig
     *                The filter configuration object
     */
    public void init(FilterConfig filterConfig) throws ServletException {
        this.filterConfig = filterConfig;
        this.encoding = filterConfig.getInitParameter("encoding");
    }

    // ------------------------------------------------------ Protected Methods

    /**
     * Select an appropriate character encoding to be used, based on the characteristics of the current request and/or
     * filter initialization parameters. If no character encoding should be set, return <code>null</code>.
     * <p>
     * The default implementation unconditionally returns the value configured by the <strong>encoding</strong>
     * initialization parameter for this filter.
     * 
     * @param request
     *                The servlet request we are processing
     */
    protected String selectEncoding(ServletRequest request) {
        return (this.encoding);
    }

}
